In the field of printing, the most common type printer has been the printer which impacts against record media that is caused to be moved past a printing line or line of printing. As is well-known, the impact printing operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechanical drive system and which system enables precise control of the impact members.
In the field of dot matrix printers, it has been quite common to provide a print head which has included therein a plurality of print wire actuators or solenoids arranged or grouped in a manner to drive the respective print wires a very short, precise distance from a rest or non-printing position to an impact or printing position. The print wires are generally either secured to or engaged by the solenoid plunger or armature which is caused to be moved such precise distance when the solenoid coil is energized and wherein the plunger or armature normally operates against the action of a return spring.
It has also been quite common to provide an arrangement or grouping of such solenoids in a circular configuration to take advantage of reduced space available in the manner of locating the print wires in that specific area between the solenoids and the front tip of the print head adjacent the record media. In this respect, the actuating ends of the print wires are positioned in accordance with the circular arrangement and the operating or working ends of the print wires are closely spaced in verticallyaligned manner adjacent the record media. The availability of narrow or compact actuators permits a narrower or smaller print head to be used and thereby reduces the width of the printer because of the reduced clearance at the ends of the print line. The print head can also be made shorter because the narrow actuators can be placed in side-by-side manner closer to the record media for a given amount of wire curvature.
In the wire matrix printer which is utilized for receipt and for journal printing operations, the print head structure may be a multiple element type and may be horizontally disposed with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner across the receipt or journal paper and wherein the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head. In the wire matrix printer which is utilized for business forms or like record media printing operation, the print head may be oriented in a manner wherein the nose is pointed downward for printing on the form, slip or like record media while the carriage and print head are moved above and across the form or like record media in the horizontal direction.
Further, in the wire matrix printer which is utilized for receipt, slip and journal printing operations, the individual print heads may be vertically oriented and printing performed by means of the print wires moving downwardly to impact on the record media. Alternatively, the individual print heads may be horizontally oriented and printing performed by means of the print wires moving horizontally to impact on the record media. A preferred number of four of such individual print heads is common in known arrangements.
In the dot matrix printer, there is a requirement for one or more small electric motors to drive certain parts of the printer. A small motor is used to drive the print head carriage in reciprocating manner in the printer that includes a stationary platen and a movable print head. The print head carriage and the associated print head are moved to appropriate and precise locations along the line of printing for dot matrix printing of alpha numeric characters or of graphics type characters. A second motor is used to drive the paper such as a receipt, a slip or a journal at the end of the printing operation and which paper drive is usually performed at the end of each line of printing. However, it is feasible to advance the paper at the end of the printing on a line without the necessity of moving the carriage and print head to the end of such line. This arrangement enables faster printing operation.
The dot matrix printer is commonly used in the form of an output device in computer systems and word processing systems. Dot matrix printers in the form of receipt printers and journal printers are used in an electronic cash register (ECR) or in a point of sale (POS) terminal.
In the dot matrix printer, predetermined characters, letters, symbols or the like are denoted with the use of "M (column) X N (row)" dots which are arranged in a matrix. In this arrangement, the print heads are classed according to the printing method, as solenoid impact type, heat transfer printing type, ink jet printing type, high frequency driving type, and laser beam type print heads.
When dots are printed with use of any of the above-mentioned print head types, the printing speed is determined by the lateral feed speed of the print head. However, it is to be noted that the lateral feed speed cannot be set to a value in excess of the response cycle or time required for driving the print head in a dot printing operation. As a result of this observation, the printing speed is proportional to the response time of the print head and the number of N dots in a row of the character, letter or symbol.
It is also to be noted that a greater number of dots or higher resolution improves the print quality, especially in the printing of Chinese characters. However, in view of the relationship between the printing speed and the print quality, there has been proposed a printing method for balancing these two parameters in the overall printing operation. The proposed printing method provides that, in the case of certain characters and letters, continued printing or printing in each and every dot position in a row is inhibited in order to speed up the lateral feed of the print head. The printing pitch is reduced in the printing of a column or in the slanted or oblique portion of the character to improve the print quality.
Representative documentation in the field of printer control includes U.S. Pat. No. 4,162,131, issued to A. B. Carson et al. on July 24, 1979, which discloses a drive circuit responsive to input pulses to supply drive energy pulses to print heads so as to produce constant impact forces and print intensity by decreasing the energy of the drive pulses as a function of the time interval between successive input pulses below a predetermined time interval.
U.S. Pat. No. 4,162,858, issued to K. Brandenburg on July 31, 1979, discloses a circuit which decides whether or not a magnet has already been actuated during printing of the previous column of the character being printed. When the magnet has not been actuated, a longer pulse or longer amount of energy is provided to the magnet for resonance with printer operation.
U.S. Pat. No. 4,291,992, issued to C. W. Barr et al. on Sept. 29, 1981, discloses a control circuit that generates a firing signal for each print pin comprising a relatively long pulse followed by a series of short pulses. The number of short pulses may be reduced when a successive pulse for the same print pin is received in the interval between the long pulse and completion of the short pulses.
U.S. Pat. No. 4,485,425, issued to M. Gruner et al. on Nov. 27, 1984, discloses a drive circuit for a print element including a drive transistor and a switching transistor each connected to a control transistor that furnishes pulses of different duration such that the switching transistor is turned off before the drive transistor.
U.S. Pat. No. 4,653,941, issued to K. Suzuki on Mar. 31, 1987, discloses a dot matrix printer having first detecting means for detecting the position of the print head, second detecting means for detecting the number of cycles of movement of the print head during printing of a dot pattern for one line, means for judging whether to permit dot printing according to outputs of the two detecting means, and driver means for driving the print head.
U.S. Pat. No. 4,713,623, issued to D. C. Mower et al. on Dec. 15, 1987, discloses a control system wherein a double column of print elements are used and no single print element is required to print more than once in any four column interval of printed text.
And, U.S. Pat. No. 4,780,006, issued to T. Hamano et al. on Oct. 25, 1988, discloses a slip printer wherein the slip is placed in an orientation that is 90 degrees from normal orientation to accommodate slips which are wider than the print station. A pattern processing section is capable of changing the arrangement of the dot pattern depending upon the orientation of the slip.